Having started the day level with Belgian Nicolas Colsaerts Kapur moved ahead when he birdied the first while his big-hitting playing partner bogeyed.
But after taking four shots to reach the green at the par four fourth, Kapur two-putted to drop to seven under.
He was joined on that mark by Spain's Gonzalo Fernandez-Castaño and US PGA Championship winner Martin Kaymer.
Fernandez-Castaño, whose last win came at the Belfry in 2008, was another to bogey the first before fighting back with three birdies.
Germany's Kaymer, looking to extend his lead in The Race to Dubai on his return to action after landing a first Major, was one under for the day after five holes.